The following invention is generally related to instrumentalities and methodologies for the non-destructive inspection, and especially for testing and evaluation of aircraft components.
Recent tragedies in aircraft transportation has caused concern over the ability of airlines to evaluate the airworthiness of aircraft within their respective fleets. As airframes age, the characteristics of the materials that constitute the airframe components change due to the stresses and strains associated with flights and landings. The material goes beyond the point of elasticity (the point the material returns to its original condition) and into the point of plasticizing or worse, beyond to failure. As a result, inspections and testing are conducted on aircraft components periodically during the aircraft""s component life cycle as are mandated by governing bodies and based largely on empirical evidence.
Currently commercial industry inspection and repair method are inefficient, costly and not standardized. Their inspection and repair procedures and processes have changed little in the past 20 or 30 years and have not solved the xe2x80x9cAging Aircraftxe2x80x9d safety problems. Inspection of aircraft components are historically limited to the xe2x80x9cTap Test,xe2x80x9d visual inspection, and Eddy Current analysis. Standardized technical repairs are nonexistent. Commercial safety integrity is continually compromised by not determining the extent of aircraft structure corrosion and fatigue.
Unfortunately, manned inspection is still the state of the art. Inspection timetables are developed and updated primarily as a function of anecdotal evidence, all too frequently based on airline catastrophes.
Inspections and testing are bificurated into two areas: destructive testing and nondestructive inspection (NDI), nondestructive testing (NDT) or nondestructive evaluation (NDE). The area of destructive testing, as the name implies, requires the aircraft component under scrutiny to be destroyed in order to determine the quality of that aircraft component. This can result in a costly endeavor because the aircraft component is destroyed even though it passed the test procedure. It is, therefore, no longer available for use. Frequently, where destructive testing is done on samples (e.g. coupons) and not on actual components, the destructive test may or may not be reflective of the forces that the actual component could or would withstand within the flight envelope of the aircraft.
On the other hand, NDI, NDT or NDE have the obvious advantage of being applicable to actual aircraft components in their actual environment. Several important methods of NDI, NDT or NDE that are performed in a laboratory setting are listed and summarized below.
Radiography. This is a general term for the inspection of a material by subjecting it to penetrating irradiation. X-rays are the most familiar type of radiation used in this technique, although good damage detection has been done using neutron radiation. Most materials used in aircraft component manufacturing are readily acceptable to X-rays. In some instances, an opaque penetrant is needed to detect many defects. Real-time X-rays are starting to be used to permit viewing the area of scrutiny while doing the procedure. Some improvement in resolution has been achieved by using a stereovision technique where the X-rays are emitted from dual devices which are offset by about 15xc2x0. When viewed together, these dual images give a three-dimensional view of the material. Still, the accuracy of X-rays is generally no better than xc2x110% void content. Neutrons (N-ray), however, can detect void contents in the xc2x11% range. The difficulty is the obvious problem with safety and radiation sources. In addition to the normal use to detect internal flaws in the metals and composite structures, X-rays and neutrons can detect misalignment of honeycomb cores after curing.
Ultrasonics. This is most common method for detecting flaws in composite materials. The method is performed by scanning the material with ultrasonic energy while monitoring the reflected energy for attenuation (diminishing) of the signal. The detection of the flaws is somewhat frequency-dependent and the frequency range and scanning method most often employed is called C-scan. In this method, water is used as a coupling agent between the sending device and the sample. Therefore, the sample is either immersed in water or water is sprayed between the signal the signal transmitter and the sample. This method is effective in detecting defects even in thick samples, and may be used to provide a thickness profile. C-scan accuracies can be in the xc2x11% range for void content. A slightly modified method call L-scan can detect stiffness of the sample by using the wave speed, but requires that the sample density be known.
Acousto-ultrasonics. This analysis method is similar to ultrasound except that separate sensors are used to send the signal and other sensors are used to receive the signal. Both sensors are, however, located on the same side of the sample so a reflected signal is detected. This method is more quantitative and portable than standard ultrasound.
Acoustic emission. In this method, the sounds emitted by a sample are detected as the sample is subjected to a stress. The stress can be mechanical, but need not be. In actual practice, in fact, thermal stresses are the most commonly employed. Quantitative interpretation is not yet possible except for well-documented and simple shapes (such as cylindrical pressure vessels).
Thermography. This method, which is sometimes call IR thermography, detects differences in the relative temperatures of the surface and, because these temperature differences are affected by internal flaws, can indicate the location of those flaws. If the internal flaws are small or far removed from the surface, however, they may not be detected. Two modes of operation are possible-active and passive. In the active mode, the sample is subjected to a stress (usually mechanical and often vibrational) and then the emitted heat is detected. In the passive mode, the sample is externally heated and the thermal gradients are detected.
Optical holography. The use of laser photography to give three-dimensional pictures is call holography. This method can detect flaws in samples by employing a double-image method where two pictures are taken with an induced stress in the sample between the times of the pictures. This method has had limited acceptance because of the need to isolate the camera and sample from vibrations. Phase locking may eliminate this problem. The stresses that are imposed on the sample are usually thermal. If a microwave source of stress is used, moisture content of the sample can be detected. For composite material, this method is especially useful for detecting debonds in thick honeycomb and foam sandwich constructions. A related method is called shearography. In this method, a laser is used with the same double exposure technique as in holography with a stress applied between exposures. However, in this case an image-shearing camera is used in which signals from the two images are superimposed to give interference and thereby reveal the strains in the samples. Because strains are detected, the size of the pattern can give an indication of the stresses concentrated in the area and, therefore, a quantitative appraisal of the severity defect is possible. This attribute, plus the greater mobility of this method over holography, and the ability to stress with mechanical, thermal, and other methods, has given this method wide acceptance since its introduction.
Even though there are a wealth of diagnostic tools, there is a need to provide systems and principled processes to execute NDI, NDT and NDE of aircraft and their constituent components to take advantage of the methods briefly described above in order to better characterize the material properties of materials used in the manufacturing of aircraft components. The present invention fulfills this need outside of a laboratory setting.
The present invention includes three robotic imaging inspection methods and technologies: real-time X-ray, N-ray and laser ultrasonics. When used separately, certain imaging inspection methods find certain aircraft structural defects. For example, the present invention""s N-ray imaging inspection methodology locates corrosion and measurable loss of structural material. The present invention""s real-time X-ray imaging inspection methodology can find the smallest of structural cracks; while the ultrasonics methodology locates defect regardless of a composite or metal structure""s configuration. When used in combination on any given aircraft or component, all structural defects and discrepancies can be located within high precision and trend analysis of future defect problems per model and series aircraft can be formulated and determined.
The following citations reflects the state of the art of which applicant is aware and is included herewith to discharge applicant""s acknowledged duty to disclose relevant prior art. It is stipulated, however, that none of these citations teach singly nor render obvious when considered in any conceivable combination the nexus of the instant invention as disclosed in greater detail hereinafter and as particularly claimed.
The present invention is directed to systems and processes that perform NDI, NDT and NDE on aircraft in whole and for components individually. One key to the present invention involves systematic, automated inspection coupled with comparison to a standard.
The term xe2x80x9caircraft componentsxe2x80x9d encompasses, but not limited to: items as small as individual fasteners, pieces, sections or strands of wiring, materials, fasteners once installed and in their environment, weld seams, sections of panels, mounts and brackets, control surfaces, landing gear, the components and pieces thereof; flight surfaces, components and pieces thereof; a powerplant, its sections, its components and pieces thereof; sections of a fuselage and its entirety; to the whole aircraft positioned in an inspection bay or hangar.
NDI, NDT or NDE systems and processes having the characteristics of the present invention constitute a structure, preferably configured as an enclosure, to contain an inspection and testing apparatus and the aircraft components under inspection. The structure is lined with shielding to attenuate the emission of radiation to the outside of the enclosure and having corbels therein to support the components that constitute the inspection and testing apparatus. The inspection and testing apparatus is coupled to the structure, resulting in the formation of a gantry for supporting a carriage and a mast mounted on the carriage. An electromagnetic radiation emitter, electromagnetic radiation detector or both are mounted on the mast which forms, in part, at least one radiographic inspection robot capable of precise positioning over large ranges of motion. The carriage is coupled to the mast for supporting and allowing translation of the at least one electromagnetic radiation emitter and detector mounted on the mast, wherein the mast is configured to provide two axes movement of the electromagnetic radiation emitter, detector or both.
The emitter, detector or both is configured to provide rotation about at least one axis of pitch, roll and yaw motion of the emitter, detector or both.
Such NDI, NDT or NDE systems and process are preferably configured wherein the emitter, detector or both are configured as a yoke to provide rotation about at least one axis of pitch and roll motion of the emitter, detector or both. The yoke could include first and second members capable of adjusting the distance between the members; whereby the first member supports a source of electromagnetic radiation and the second member supports at least one of an electromagnetic radiation detector or an imaging device.
An NDI, NDT or NDE system or process having the characteristics of the present invention preferably contains the steps to perform the method for the non-destructive inspection and testing of aircraft components including a database comprising at least one profile of a prototypical aircraft component, maintaining an enclosure at constant environmental conditions, placing at least one aircraft component into the enclosure and allowing sufficient time to permit the aircraft component to reach the constant environmental conditions, precisely placing reference markers on specific areas of the aircraft component, reading the location of the reference markers, comparing the reading with the at least one profile and reporting the resultant of the comparison. The reference markers introduce the aircraft to the system and can uncover gross distortions in the aircraft""s geometry, and aircraft location.
Further characteristics of the present invention include a gantry robot having a yoke to which an attached scanning apparatus provides the capability to reposition the yoke and scanning apparatus without the need for disassembly. The joints of the yokes are configured so as to be capable of articulation such that each leg of the yoke may be raised or lowered. By allowing each leg of the yoke to be raised or lowered, the scanning apparatus may be used to scan areas of an intact aircraft that would otherwise be difficult or impossible to scan.
As previously stated the present invention has one or more robots. The use of multiple robots provides several advantages. Firstly, multiple robots allow simultaneous inspection of several areas of an aircraft, thereby reducing the time required to inspect an aircraft. Secondly, multiple robots avoid the need for a single long supporting beam, which would reduce positioning accuracy and repeatability. Thirdly, multiple robots allow each robot to be specifically designed to inspect particular areas of an aircraft, thereby allowing accommodation of special attributes of the various areas.
A structure is provided to contain inspection apparatus and items under inspection and defines an enclosure. The structure comprises walls, a ceiling, and a floor. A hanger door entrance is defined in a wall. The hanger door entrance is equipped with a hanger door. The walls, ceiling, and hanger door are designed to attenuate x-ray radiation and neutron radiation.
Corbels are provided to support multiple robots. The walls, ceiling, and hanger door entrance are designed to support the corbels, which provide x-axis translation. The structure is designed to accommodate structural loading while maintaining accuracy and repeatability of robot position over six axes of movement within a narrow range of tolerances better than xc2x10.250 inches, and preferably better than xc2x10.160 inches. The structure accommodates structural loading of various types, for example floor loading, wind loading and loading from the mass of the robots.
One embodiment of the invention includes a plurality of carriages on a single beam. For example, one carriage may provide support and translation of a robot for n-ray radiography, and another carriage may provide support and translation for a robot for x-ray radiography.
The inspection facility is designed to protect personnel from radiation hazards (including X-rays and neutrons). Shielding, including shielding of walls, doors, and windows is provided. Interlocks are provided to prevent the emission of radiation when personnel might be endangered, such as when a door is opened. Other measures, such as key controls and password authentication are provided to prevent emission of radiation or other potentially hazardous activities, such as motion of robotic systems, without approval of authorized personnel. Radiation monitoring and alarm systems are provided to detect abnormal radiation levels and provide warning.
One example of a technique used to provide shielding is the penetration shielding areas (for example, walls, doors, floors, ceilings, windows, etc.) at an angle sufficient to ensure that any radiation substantially perpendicular to the plane of the shielding material will be incident upon the shielding material of which the shielding area is constructed. This technique avoids the need to add additional shielding material, such as by packing a perpendicularly bored hole with additional shielding material.
A method for design of a non-destructive inspection, testing and evaluation system for aircraft and components having a precision robotic system is provided. The dimensional and structural requirements of a building are determined, and a preliminary design for the building is made. The preliminary design for the building is analyzed to identify any frequencies at which such a building might resonate. For example, a technique such as finite element analysis may be employed. Based on the results of the analysis, the preliminary design of the building may be modified to correct any deficiencies.
The dimensional, structural, and functional requirements for robots to be housed within the building are determined, and a preliminary design of the robots is made. The preliminary design of the robots is analyzed to identify any frequencies at which such robots might resonate. Any interaction between the resonant frequencies of the building and the resonant frequencies of the robot are analyzed. Based on the results of the analysis, the preliminary design of either or both of the building and the robots may be modified to correct any deficiencies.
The dimensional, structural, and functional requirements of any end effectors mounted on the robots are determined, and a preliminary design of the end effectors is made. The preliminary design of the end effectors is analyzed to identify any frequencies at which such end effectors might resonate. Any interruption between other elements, such as the building or the robots, is analyzed. Based on the results of the analysis, the preliminary design of any or all of the building, robots, or end effectors may be modified to correct any deficiencies.
Another factor to be considered is the type of earthquake region in which the facility is to be located. Different earthquake regions may exhibit earthquakes having different characteristics, for example earthquakes having vibration and motion of predominantly a certain frequency range. This frequency range is determined for the location at which the facility is to be located based on geological data. The preliminary designs of the building, robots, and end effectors is analyzed base on anticipated excitation from earthquakes. Based on the results of the analysis, the preliminary design of any or all of the building, robots, or end effectors may be modified to correct any deficiencies.
When the preliminary designs of the buildings, robots, and end effectors are completed, modeling of the entire system may be performed to assure accuracy and repeatability of robot positioning. Oscillatory excitation of the system components resulting from robot motion and acceleration and deceleration may be analyzed. Designs of the system components may be modified to maximize desirable characteristics, such as accuracy and repeatability of robot positioning, while minimizing undesirable characteristics, such as unwanted oscillatory excitation of system components.
The major assemblies of the non-destructive inspection and testing structure are the structure itself, preferably a building and further defining an enclosure, and the inspection and testing apparatus. A structure is provided to contain the inspection and testing apparatus and the items under inspection or testing. The structure is preferably composed of walls, floor, a ceiling and a hanger door. The walls, ceiling and hanger door are designed to attenuate X-ray radiation and neutron radiation. Corbels are provided to support the multiple robots. The walls, ceiling and hanger door entrance are designed to support the corbels thus permitting translation across the items under inspecting, testing or evaluation. The structure is designed to accommodate structural loading while maintaining accuracy and repeatability of the robot positions, i.e., the inspection and testing apparatus over six axes of movement within a narrow range of tolerances better than plus or minus 0.25 inches and preferably better than plus or minus 0.16 inches. The structure accommodates structural loading of various types, for example, floor loading, wind loading and loading from the mass of the robot.
The non-destructive inspection and testing system for aircraft components is capable of precise positioning over large ranges of motion. The non-destructive inspection and testing system for aircraft components comprises a beam arrangement for supporting and allowing translation of a carriage. The beam is mounted on rails which are attached to the facility corbels by the means of end trucks, providing movement along the length of the facility or X axes. The carriage moves along the length of the beam providing Y axes, and a telescoping tube or mast is attached to the carriage in a vertical position, providing Z axes. At the bottom of the mast, three axes of movement are provided, pitch, rotate, and yaw of the yoke to which the inspection apparatus is attached. The translations permit the system to scan the intact aircraft to the component level. The carriage is coupled to a mast structure for supporting and allowing translation of a yoke. The mast comprises a plurality of tubes that can move telescopically to provide a large range of motion in a vertical direction while supporting large amounts of mass. In one embodiment of the invention, the beam arrangement is located overhead, for example, near the ceiling of the building. The building and beam arrangement form a gantry for supporting the carriage and structure as well as the yoke which is mounted on the mast 40. In the preferred embodiment the yoke includes two members that may be extended for example telescopically to adjust the throat depth of the yoke. Also, one embodiment of the yoke is configured to accommodate surfaces that change the camber of the wing. In particular configurations the first member supports a beam source and the second member supports an imaging device. In an alternative embodiment the mast supports a laser ultrasonic scanner. This laser ultrasonic scanner is attached to the mast of the inspection and testing apparatus and configured with rotational axes to allow scanning in a plurality of directions across complex surfaces of the aircraft or aircraft components.
Real-time X-ray radiography is accomplished in motion utilizing multi-axis movement of robots to scan at the rate of one to three inches per second and at three to five times magnification. Any pendulum or sway effect at the bottom of mast (with yoke attached) causes the real-time radiography image to be un-focus, distorted and unreadable to the operator. The problematic pendulum or sway effect is caused by two separate resonating frequencies: the first is the fundamental frequency of the robot based upon the mass and rigidity of the robot structure; and the second is the robot mounting to the housing facility which has its own resonating frequency when the robot is in motion or multiple of robot in motion or work. Providing two separate parallel bridges mounted to single end trucks with carriage straddling both parallel bridges and the mast located between the two separate bridges yields acceptable results so long as the length of the bridge does not exceed a certain length, typically fifty feet. Providing a single rail bridge typically permits a length of the bridge not to exceed ninety-six feet.
Existing hangar structure would have to be modified or new facilities would have to be built to attenuate any pendulum effect and resonating frequencies that could distort robotic inspection readings. Facility modification or new design would be based upon three separate requirements: seismic; resonate frequency of the facility with the robots in motion and the robotic envelope. Site surveys would determine the seismic activity, ground water location, type of soil, soil compaction and would result in building the facilities foundation as an isolation pad. The resonate frequency of the facility with the robots in a static positions are modeled to evaluate the pendulum effect of the robots and to determine the amount of reinforcement of steel and concrete needed to meet frequency requirements for the facility""s bearing walls. At issue is the facilities hangar door. As the robots are moved closer to the hangar door, the pendulum effects become unacceptable. Therefore, modification to the hangar door are needed to the effect of providing a steel and concrete header above the door; while, below the ground level provide a lateral tie or footer. Such modifications rigidify the side of the structure containing the hangar door to attenuate any resonate frequencies to acceptable levels for the inspection of aircraft with the robots. The robot envelope is determined by the type of aircraft that would be inspected within the facility. The envelope is factored in and any resonate frequencies are attenuated in order to provide inspection accuracy and repeatability.
Inspection of aircraft wings require the control surfaces to be extended to allow for a total wing inspection. This wing configuration causes sharp radial surface turns at the fore and aft ends of the wings"" leading and trailing edge surfaces and the inability for a normal xe2x80x9cCxe2x80x9d shaped yoke to conform to these areas to perform a total inspection perpendicular to the part under inspection. The solution to this problem is to provide a modified xe2x80x9cCxe2x80x9d shaped yoke with the lower arm having an articulating member, akin to a double joint, in order to allow the lower arm to tuck underneath the control surface.
Further characteristics of the present invention include a gantry robot having a yoke to which an attached scanning apparatus provides the capability to reposition the yoke and scanning apparatus without the need for aircraft disassembly. The joints of the yoke are gimbaled, so as to be capable of articulation, such as each leg of the yoke allows both sender and receiver to maintain perpendicular alignment to each other. By allowing each leg of the yoke to be raised or lowered, the scanning apparatus may be extended, used to scan areas of an intact aircraft that would otherwise be difficult or impossible to scan. Yoke configuration also includes telescoping legs to allow the throat depth to change. This change in depth is needed to reach points on an aircraft""s wing where the wing root may exceed 27 feet and where the outer part of the wing is approximately four feet across.
Accordingly, it is a primary object of the present invention to provide a new, novel and useful Non-Destructive Inspection, Testing and Evaluation System for Intact Aircraft and Components and method therefore.
It is a further object of this invention to provide a method and apparatus as characterized above which accurately forecasts the need for corrective measures in a timely manner.
It is a further object of this invention to provide a method and apparatus which is easy to use and minimize the need for highly experienced personnel.
It is a further object of this invention to provide a method and apparatus where the diagnosis is repeatable.
It is a further object of this invention to provide a method and apparatus where the system and method can be reliably replicated.
It is a further object of this invention to provide a method and apparatus where the results from individual inspectors can be subsequently incorporated into a trend analysis data base.
It is a further object of this invention to provide a method and apparatus where the analysis does not mandate destruction of the item examined.
These and other objects will be made manifest when considering the following detailed specification when taken in conjunction with the appended drawing figures.